The dispatcher calls an operating system function to determine the name of the assigned server for an IP address. While this function is running, the dispatcher, and, therefore, the entire instance, is blocked.
The dispatcher tries to determine the name of the affected server or the GUI terminal when it issues error messages. To do this, the dispatcher uses a reverse name lookup. This is available as an operating system function. During the runtime of this operating system function, the dispatcher is blocked. If it takes several seconds or minutes for the operating system to determine the name or the fact that a name cannot be determined, a standstill of the affected instance may occur.
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The dispatcher automatically deactivates the reverse name lookup as soon as it takes longer than 10 seconds. The system then writes the following entries in the trace file dev_disp:
*** WARNING => NiAddrToHost took x seconds
DpAddrToHost: Disabling reverse name lookup
The value of the profile parameter rdisp/reverse_name_lookup is 0 in RZ11.
This response is active as of the following patch levels:
In any case, you can deactivate the Reverse Name Lookup manually by setting the profile parameter
rdisp/reverse_name_lookup = 0
This is possible at runtime since this is a dynamic parameter.